JPH08149U - Printed board - Google Patents

Abstract

(57) Abstract: It is possible to prevent a defective connection between a through-hole conductor and a circuit pattern formed of carbon paint. A conductive pattern (4 ') for power distribution and fixed contact patterns (3, 3') for key switches are formed on one surface of an insulating substrate (1) with carbon paint. The copper foil circuit 2 is formed on the other surface of the insulating substrate 1. A predetermined portion of the copper foil circuit 2 and a predetermined portion of the conductive pattern 4'are connected by a through hole conductor 5 penetrating the insulating substrate 1. Conductive pattern 4
′ And the fixed contact patterns 3 and 3 ′ for the key switch are formed after forming the through-hole conductor 5.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 The present invention relates to a printed circuit board having a fixed contact pattern made of carbon paint for a key switch and a conductive pattern for wiring on one side of an insulating board, and a copper foil circuit on the other side of the insulating board. is there.

[0002]

[Prior art]

 In this type of conventional printed circuit board, the fixed contact pattern and conductive pattern for the key switch and the copper foil circuit are provided on the same surface of the board.Therefore, electronic components such as capacitors and transistors are mounted on the board and flow soldering is used. When soldering each electronic component to the copper foil circuit, it was necessary to take measures to prevent the solder from adhering to the fixed contact pattern provided in the exposed state. Therefore, conventionally, the fixed contact pattern is masked with a semiconductor resist film, and after the soldering process of the electronic component is completed, the resist film is removed to expose the fixed contact pattern. Recently, fixed contact patterns have been formed with carbon paint.Since the conductive pattern for wiring this fixed contact pattern to a predetermined part of the circuit was formed with silver paint, these patterns are printed. It was necessary to perform each in a separate process.

As described above, the conventional printed circuit board of this type requires an extra step of masking the fixed contact pattern, and also needs a step of removing the masking after mounting the electronic parts. Also, since the conductive pattern needs to be formed in different steps, there is a drawback that the number of steps is increased and the cost is increased.

In order to overcome this drawback, the inventor has formed a fixed contact pattern for key switches and a conductive pattern for wiring on one surface of an insulating substrate, and a copper foil circuit on the other side of the insulating substrate. It was considered to form it only on the surface, form the fixed contact pattern for the key switch and the conductive pattern with carbon paint, and connect the copper foil circuit and the conductive pattern with the through-hole conductor penetrating the substrate. When a conventional double-sided circuit board is manufactured, as in the printed circuit board disclosed in Japanese Utility Model Laid-Open No. 54-64958, a through-hole is formed at the same time as the circuit pattern is formed on both surfaces of the board or after the circuit pattern is formed. A conductor is formed to connect the circuit patterns on both sides of the substrate.

[0005]

[Problems to be solved by the device]

 When a conductive circuit pattern is formed using silver paint as in the printed circuit board disclosed in Japanese Utility Model Laid-Open No. 54-64958, the circuit pattern is formed on both sides of the board at the same time as or when the circuit pattern is formed. There was no problem even if the through-hole conductor was formed after the formation. However, when forming fixed contact patterns for key switches and conductive patterns with carbon paint, if through-hole conductors are formed after circuit patterns are formed on both sides of the board as in the conventional case, sufficient through-hole conductors are formed. There is a problem that cannot be done. For example, if the circuit pattern is formed so that the end of the pattern extends to the position just before the opening end of the through hole, carbon paint may partially flow into the opening end of the through hole when the circuit pattern is formed. become. However, the surface of the inflow portion formed by curing the carbon paint is relatively unsuitable for the conductive paint for forming the through-hole conductor such as silver paint. Therefore, when a through-hole conductor is formed later by using a conductive paint such as silver paint, the conductive paint for forming the through-hole conductor is removed from the inflow part formed by the carbon paint formed in the through hole. There is a high possibility that it will run off, and a poor connection will easily occur between the circuit pattern and the through-hole conductor. It is possible to form a circuit pattern by using carbon paint so that the open end of the through hole is left, but in this case, the conductive paint for forming the through hole conductor is formed by the corner of the open end of the through hole. There is a possibility of breakage, and even in this case, poor connection between the circuit pattern and the through-hole conductor is likely to occur.

An object of the present invention is to provide a printed circuit board that is less likely to cause a connection failure when forming a circuit pattern with carbon paint.

[0007]

[Means for Solving the Problems]

 In the present invention, a carbon coating is used to form a conductive pattern for power distribution and a fixed contact pattern for a key switch on one surface of the insulating substrate. A copper foil circuit is formed on the other side of the insulating substrate. A predetermined portion of the copper foil circuit and a predetermined portion of the conductive pattern are connected by a through-hole conductor that penetrates the insulating substrate. In the present invention, in particular, the conductive pattern and the fixed contact pattern for the key switch are formed after forming the through-hole conductor.

If the through-hole conductor is formed first, a part of the conductive pattern formed by using the carbon paint is formed so as to cover the end portion of the through-hole conductor, so that the conductive pattern and the through-hole conductor are formed. There is no possibility of a poor connection between the and.

[0009]

[Embodiment of device]

 An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an embodiment of the present invention, in which 1 is an insulating substrate composed of a paper phenol laminated plate, a paper epoxy laminated plate, a glass epoxy laminated plate, etc. A copper foil circuit 2 having a predetermined pattern is formed on one surface of the insulating substrate 1 by etching. On the other surface of the substrate 1, fixed contact patterns 3 and 3 ′ for key switches and conductive patterns 4 and 4 ′ for wiring for connecting these patterns to predetermined locations on the substrate are both carbon paint ( It is formed by adding carbon powder to a resin binder. If both the fixed contact patterns 3 and 3'and the conductive patterns 4 and 4'are made of carbon paint in this way, both patterns can be formed by one printing, and the number of steps can be reduced. The terminal portions 4a and 4'a of the conductive patterns 4 and 4'that can be connected to the copper foil circuit are connected to predetermined portions of the copper foil circuit 2 by the through-hole conductors 5 provided through the holes 1a penetrating the substrate 1. Has been done. In the illustrated example, the through hole conductor 5 is provided before the conductive patterns 4 and 4 ′ are formed, and the conductive patterns 4 and 4 ′ are arranged so that the terminal portions 4 a and 4 a ′ overlap the ends of the through hole conductor 5. It is printed. A portion of the copper foil circuit 2 that avoids the adhesion of solder is covered with a solder resist 6.

The conductive patterns 4 and 4 ′ are covered with an insulating protection layer 7 formed by printing. Sharp edges are formed at the corners of the pattern of the copper foil circuit 2 formed by etching. However, if the insulating protective layer 7 is formed on the conductive patterns 4 and 4 ', the conductive patterns 4 and 4'formed from a mechanically weak carbon coating can be protected, so that the printed circuit boards are stacked. Even if it is transported in the state, the conductive pattern is not cut by the sharp edge of the copper foil circuit 2 on another printed board. In particular, since the conductive patterns 4 and 4'are formed so as to cover the ends of the through-hole conductors 5, the conductive patterns are less likely to be cut, and in the present embodiment, all of the through-hole conductors 5 are insulated. Since it is covered with the protective layer 7, the conductive patterns 4, 4 ′ are hardly cut. Further, since the conductive pattern 4'is formed so as to cover the end portion of the through-hole conductor 5, it projects considerably above the fixed setting pattern 3, 3'on the end portion of the through-hole conductor 5. Therefore, when this protrusion is overlapped with another printed substrate, it functions as a spacer means. Therefore, disconnection of the fixed contact pattern can be reliably prevented. According to the present embodiment, the conductive pattern and the fixed contact pattern for the key switch are formed by the carbon coating, but the carbon paint on the through-holes or the carbon paint on the contacts is rubbed and scattered. Can be prevented. Further, even if the carbon paint of the contact is scattered, it does not have a bad influence on the conductive patterns.

Although not shown, on the surface of the substrate 1 on which the fixed contact patterns 3 and 3 ′ and the conductive patterns 4 and 4 ′ are provided, as many other fixed contact patterns and conductive patterns as necessary are provided. It is provided. Further, a hole (not shown) for mounting an electronic component is provided through a predetermined portion of the substrate 1 and the copper foil circuit 2, and the copper foil circuit is provided with the electronic component lead wire inserted in this hole. By applying flow soldering to the exposed surface, electronic components are soldered to the copper foil circuit. In this case, since the fixed contact patterns 3, 3'and the conductive patterns 4, 4'are on the surface opposite to the copper foil circuit 2, solder does not adhere to these patterns. Therefore, it is not necessary to mask the fixed contact pattern and the conductive pattern for wiring.

As described above, when both the fixed contact pattern and the conductive pattern are formed of carbon paint, it is inevitable that the operating resistance of the key switch becomes 500Ω or more, but in most cases, the key switch is “1”. Since it suffices to be able to selectively obtain the state of “0” and “0”, even if there is an operating resistance of this level, no problem occurs in almost all cases.

In the above embodiment, the fixed contact patterns 3 and 3 ′ are formed in a U shape, but the shape of this fixed contact pattern is arbitrary, and the movable contact of the key switch, such as a comb blade shape or a T shape. It can be formed into an appropriate shape that is easy to contact with.

In the above embodiment, it goes without saying that other patterns such as a printing resistor and a resistor for a variable resistor can be further provided on the surface of the substrate 1 on which the fixed contact pattern is provided, if necessary. .

According to the above-described embodiment, since the conductive pattern is formed so as to cover the end portion of the through-hole conductor, the contact area between the through-hole conductor and the conductive pattern is increased and the disconnection is less likely to occur. Also, by forming a conductive pattern and an insulating protection layer on the protruding end of the through-hole conductor, it is possible to form a protruding portion that is significantly protruding from the surface of the substrate. Acts as a spacer to and from the board, greatly reducing the chances of a copper foil circuit edge on the other side of another board breaking a contact pattern not covered by an insulating protective layer be able to.

[0017]

[Effect of device]

 According to the present invention, since the conductive pattern and the fixed contact pattern for the key switch are formed by using the carbon paint after forming the through-hole conductor, the connection failure does not occur between the conductive pattern and the through-hole conductor. There are advantages.

[Brief description of drawings]

FIG. 1 is a plan view showing a main part of an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a cross-section taken along line II-II of FIG. 1 with a part thereof omitted.

[Explanation of symbols]

 1 Insulation board 2 Copper foil circuit 3, 3'Fixed contact pattern for key switch 4, 4 'Conductive pattern 5 Through hole conductor

Claims (1)

[Scope of utility model registration request] 1. A conductive pattern for power distribution and a fixed contact pattern for a key switch are formed on one surface of an insulating substrate by carbon paint, and a copper foil circuit is formed on the other surface of the insulating substrate. A printed circuit board obtained by connecting a predetermined portion of the conductive pattern and a predetermined portion of the conductive pattern by a through-hole conductor penetrating the insulating substrate, after forming the through-hole conductor with the conductive pattern and the fixed contact pattern for a key switch. A printed circuit board characterized by being formed.